In Crohn's disease, enterovesical fistula is an uncommon but potentially dangerous complication. It is the most frequent form of urinary tract fistula, most likely due to the close proximity of the ileal loops and the bladder. It is important to be aware of this complication because it can be the initial manifestation of Crohn's disease. The required treatment in most cases is surgical (suture of bladder wall and resection of the involved bowel segment).